Anodizing-assisted grinding device and anodizing-assisted grinding method

Abstract

To efficiently perform grinding while more efficiently anodizing the surface of a workpiece.SOLUTION: An anodized film is formed on the surface of a workpiece 1 by passing a direct current between an anode 6, a cathode 7, and the workpiece 1 via an electrolyte W, and the anodized film is ground away by a grinding wheel 12. The anode 6 is provided separately from the grinding wheel 12, and power is supplied while the anode 6 is pressed against the workpiece 1 by pressure applied by pressure applying means 16. The anode 6 is made of a conductive material that is softer than the workpiece 1. The electrolyte W is supplied from the electrode 6, 7 sides of the anode 6 and the cathode 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an anodizing-assisted grinding device and an anodizing-assisted grinding method that utilizes an anodizing reaction that occurs on the surface of a workpiece when a direct current is passed through the workpiece via an electrolyte to grind the surface of the workpiece with a grinding wheel. [Background technology]

[0002] Conventionally, anodization-assisted grinding devices have been used as surface grinding devices for surface grinding workpieces such as SiC wafers (Patent Document 1). This anodization-assisted grinding device is equipped with a container for storing an electrolyte, and when processing the workpiece, the workpiece is immersed in the electrolyte stored in the container, and a direct current is passed between the anode, cathode, and workpiece via the electrolyte, and the anodization reaction that occurs on the surface of the workpiece is utilized to grind the surface of the workpiece with a grinding wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-27359 Summary of the Invention [Problem to be solved by the invention]

[0004] In such an anodization-assisted grinding device, even when grinding workpieces such as SiC wafers, the surface of the SiC wafer becomes soft due to anodization, so it becomes possible to use grinding wheels made of general abrasives such as cerium oxide or loose abrasives. Compared to grinding with a diamond grinding wheel, this has the advantage of reducing damage to the surface of the SiC wafer, improving surface roughness after processing, and reducing tool costs by using a non-superabrasive grinding wheel.

[0005] However, in conventional anodizing-assisted grinding devices, the workpiece is immersed in an electrolyte stored in a container, which makes the entire grinding device large and complex. In addition, the grinding chips generated when the workpiece is ground with the grinding wheel accumulate in the electrolyte in the container, making it difficult to collect the grinding chips and perform maintenance.

[0006] Therefore, the present inventors proposed a new anodizing-assisted grinding device in Japanese Patent Application No. 2022-71617. Unlike conventional anodizing-assisted grinding devices in which the workpiece is immersed in an electrolyte stored in a container, the anodizing-assisted grinding device according to this prior application does not require a container for storing the electrolyte by supplying the electrolyte in a flowing manner between the cathode and the workpiece, which has the advantages of making the entire device smaller and facilitating maintenance by eliminating the need to collect grinding waste that accumulates in the container.

[0007] However, the anodizing-assisted grinding device of the prior application uses a grinding wheel as an anode and supplies power through this grinding wheel, which causes the grinding wheel itself to undergo an oxidation reaction, reducing the grinding efficiency of the grinding wheel and causing a large loss of electrical energy when anodizing the surface of the workpiece. As a result, it was not possible to efficiently anodize the surface of the workpiece while efficiently grinding the surface of the workpiece with the grinding wheel.

[0008] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, an object of the present invention is to provide an anodizing-assisted grinding apparatus and an anodizing-assisted grinding method that can efficiently grind the surface of a workpiece while more efficiently anodizing the surface. [Means for solving the problem]

[0009] The anodizing-assisted grinding device according to the present invention is an anodizing-assisted grinding device that generates an anodized film on the surface of a workpiece by passing a direct current between an anode, a cathode, and the workpiece via an electrolyte, and grinds the anodized film with a grinding wheel, and power is supplied to the anode, which is provided separately from the grinding wheel, while pressing the anode against the workpiece by applying pressure. The anode is preferably made of a conductive material that is softer than the workpiece. The electrolyte is preferably supplied from the electrode side of the anode and the cathode.

[0010] The anodizing-assisted grinding method according to the present invention includes a step of generating an anodized film on a surface of a workpiece by passing a direct current between an anode, a cathode, and the workpiece through an electrolyte, and a step of grinding the anodized film with a grinding wheel, in which the anode, which is provided separately from the grinding wheel, is pressed against the workpiece by a pressure while power is supplied. The anode may be controlled to be in contact with the workpiece or out of contact with the workpiece depending on the stage of grinding the workpiece. Effect of the Invention

[0011] According to the present invention, power is supplied while an anode provided separately from the grinding wheel is pressed against the workpiece by applying pressure, which has the advantage that the surface of the workpiece can be more efficiently anodized while being ground more efficiently compared to the case where power is supplied via the grinding wheel. [Brief description of the drawings]

[0012] [Figure 1] 1 is an elevational view of an anodizing-assisted grinding device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the anodizing-assisted grinding apparatus. [Diagram 3] FIG. 2 is a cross-sectional view of a main part of the anodizing-assisted grinding apparatus. [Figure 4] FIG. 2 is a plan sectional view of a main part of the anodizing-assisted grinding apparatus. [Diagram 5] 10(a) and 10(b) are cross-sectional views of the same electrode. [Figure 6] 1(a) and 1(b) are plan sectional views of an oscillating type anodizing-assisted grinding device showing a second embodiment of the present invention. [Figure 7] FIG. 4 is a cross-sectional view of an anode showing a third embodiment of the present invention. [Figure 8] FIG. 11 is a plan sectional view of a main portion showing a fourth embodiment of the present invention. [Figure 9] FIG. 13 is an explanatory diagram of a first processing example showing a fifth embodiment of the present invention. [Figure 10] FIG. 11 is an explanatory diagram of the second processing example. [Figure 11] FIG. 11 is an explanatory diagram of the third processing example. [Figure 12] FIG. 1(a) is a diagram showing the configuration of the electrode, and FIG. 1(b) is an explanatory diagram of a fourth processing example of the electrode. BEST MODE FOR CARRYING OUT THEINVENTION

[0013] Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings. Figs. 1 to 5 show a first embodiment of an anodizing-assisted grinding device adopted in a surface grinding machine. As shown in Figs. 1 and 2, this anodizing-assisted grinding device comprises a workpiece rotating device 2 on whose upper surface a disk-shaped workpiece 1 is concentrically and detachably mounted and which rotates around a vertical axis 2a in the direction of arrow a in Fig. 1, a grindstone spindle 3 which rotates around a vertical axis 3a in the direction of arrow b in Fig. 1 and can move forward and backward in a vertical direction (the vertical direction is synonymous with the vertical direction; the same applies below), a grinding wheel 5 which is detachably mounted on a grindstone spindle flange 4 at the lower end of the grindstone spindle 3 and which can grind the upper surface of the workpiece 1 on the workpiece rotating device 2, and a grinding wheel 5 which is disposed in the vicinity of the outer periphery of the workpiece 1 on the workpiece rotating device 2. the anode 6 which is pressed against the upper surface of the workpiece 1 by pressure and which is movable relative to the rotational direction of the workpiece 1; a cathode 7 which is disposed between the grinding wheel 5 and the anode 6 and which is disposed above the workpiece 1 on the workpiece rotating device 2 in a non-contact state with a small gap S; an electrolyte supplying means 8 which is disposed on the outer periphery of the workpiece 1 with respect to the electrodes 6, 7 of the anode 6 and the cathode 7 and which supplies an electrolyte W in a flowing manner between the workpiece 1, the anode 6 and the cathode 7; and a DC power source 9 which passes a DC current from the anode 6 through the workpiece 1 to the cathode 7 via the electrolyte W.

[0014] In this anodizing-assisted grinding apparatus, the grinding wheel 5, anode 6, cathode 7, electrolyte supply means 8 and the like constitute an upper unit U1, and the workpiece rotation device 2 and the like constitute a lower unit U2.

[0015] The workpiece rotating device 2 is adapted to suction the workpiece 1 in a freely detachable manner by means of chuck means 10 at the upper end. The chuck means 10 has a porous suction plate that suctions the workpiece 1. The workpiece 1 is, for example, a conductive SiC wafer, but may be any other conductive material.

[0016] The grinding wheel 5 constitutes a grinding wheel (grinding means) for grinding the workpiece 1, and has a grinding wheel base material 11 that can be detachably attached to the underside of the grinding wheel shaft flange 4, and a non-conductive cup-shaped grinding wheel 12 fixed to the underside of the grinding wheel base material 11. The cup-shaped grinding wheel 12 has an outer diameter equal to or larger than the outer diameter of the workpiece 1, and is arranged so that the cutting edge width passes through the center of the workpiece 1. A non-conductive grinding wheel such as a general grinding wheel is used as the cup-shaped grinding wheel 12. It is also possible to use a grinding wheel other than the cup-shaped grinding wheel 12, and a grinding wheel other than a general grinding wheel, a grinding wheel having conductivity, etc. may be used depending on the material of the workpiece 1.

[0017] The anode 6 is a vertical rod-like member, and is made of a conductive material softer than the workpiece 1 so as not to damage the workpiece 1 even when it slides over the workpiece 1. The anode 6 is held by a holding case 14 and an anode holder 15 so as to be movable up and down, as shown in Fig. 3, and is pressed downward onto the workpiece 1 by a spring-type pressure means 16, and can be lifted by an air-type lifting means 17 against the pressure means 16 to a non-contact state away from the workpiece 1. The anode 6 is connected to the positive potential terminal of the DC power source 9 via a power supply member 18, the anode holder 15, and a positive potential power supply line 19.

[0018] The anode 6 and the cathode 7 constitute a power supply device. A closed circuit constituted by the DC power source 9, the anode 6, and the cathode 7 via the workpiece 1 and the electrolyte W supplies DC current to the workpiece 1 to produce an anodized film on the surface of the workpiece 1.

[0019] The anode 6, the cathode 7, and the electrolyte supply means 8 are provided on a support member 21. The support member 21 is supported by a pair of guide shafts 26 of a swinging frame 25 via a bracket 23 and a sliding portion 24 so as to be slidable in the vertical direction, and can be raised and lowered by driving an elevation drive means (not shown). The swinging frame 25 is supported so as to be swingable about a vertical axis, and can swing between a processing position (position shown in FIGS. 1 and 2) where the anode 6, the cathode 7, and the electrolyte supply means 8 are located on the workpiece rotating device 2, and a retracted position away from and to the side of the workpiece rotating device 2.

[0020] 2, the anode 6, cathode 7, and electrolyte supply means 8 are arranged in a line in the order of the grinding wheel 5, cathode 7, anode 6, and electrolyte supply means 8 on a line segment X passing through approximately the center of the workpiece 1 at the machining position. The anode 6 is arranged with the cathode 7 sandwiched between it and the grinding wheel 5, and corresponds to the outer periphery of the workpiece 1.

[0021] 3 and 4, the anode 6 is held by a bush 27 in an insulating holding case 14 so as to be vertically slidable, and has a brim-shaped piston portion 28 located above the bush 27, and a convex portion 29 that protrudes downward from the holding case 14 and can come into contact with the upper surface of the workpiece 1. A power supply member 18 capable of coming into contact with the upper end side of the anode 6 is contained within the anode holder 15, and a coil spring 30 is interposed between this power supply member 18 and the top of the anode holder 15. The holding case 14 and the anode holder 15 are detachably attached to a support member 21.

[0022] The pressurizing means 16 is composed of the anode holder 15, a coil spring 30, etc. The lifting means 17 is composed of a cylinder chamber 31 formed between the bush 27 and the piston portion 28 in the holding case 14, an air pipeline 32 connected to the cylinder chamber 31, and the coil spring 30. The air pipeline 32 is connected to an air source 39 via a control valve 33.

[0023] The anode 6 can be switched between a contact state in which it is in contact with the workpiece 1 (see Figs. 1 and 3) and a non-contact state in which it is separated from the workpiece 1 (see Fig. 5(b)) by the raising and lowering operation of the lifting means 17 by operating the control valve 33. That is, when the control valve 33 is operated to the up position, air is supplied into the cylinder chamber 31 of the lifting means 17 through the air pipe 32, so that the anode 6 rises through the piston portion 28 and the protrusion 29 separates from the top surface of the workpiece 1 to enter a non-contact state, as shown in Fig. 5(b). When the control valve 33 is operated to the down position, the air in the cylinder chamber 31 of the lifting means 17 is released by the pressure applied by the coil spring 30, and the anode 6 enters a contact state in which it is in contact with the workpiece 1, as shown in Fig. 3.

[0024] Therefore, by operating the control valve 33 according to the processing status of the workpiece 1, the lifting means 17 operates in the upward or downward direction, and it is possible to arbitrarily select a contact state in which the anode 6 is in contact with the workpiece 1, or a non-contact state in which the anode 6 is separated from the workpiece 1.

[0025] The anode 6 is made of graphite or carbon, which is softer than the workpiece 1, or a composite material thereof. However, the anode 6 may be made of any material softer than the workpiece 1, and is not limited to graphite or carbon.

[0026] The cathode 7 is flat and arranged substantially parallel to the upper surface of the workpiece 1 with a predetermined gap, for example, a minute gap S, between the cathode 7 and the upper surface of the workpiece 1. The cathode 7 is shaped so that it can face substantially the entire upper surface of the workpiece 1 from the outer periphery to the center as the workpiece 1 rotates on the workpiece rotating device 2. That is, as shown in FIG. 2, the cathode 7 is substantially semicircular having a long side 7a in the substantially diametric direction of the workpiece 1 on the side closer to the grinding wheel 5 and an arc-shaped portion 7b on the opposite side of the grinding wheel 5 with respect to the long side 7a, and a substantially V-shaped notch 7c is provided on the center side of the arc-shaped portion 7b toward the grinding wheel 5. An anode unit including the anode 6, a holding case 14, etc. is arranged inside the notch 7c.

[0027] In other words, the cathode 7 has a shape and size corresponding to approximately half of the workpiece 1 on the anode 6 side, and is provided with a pair of cathode portions 7d on both sides of the line segment X, each of which has a shape expanding toward the outer periphery of the workpiece 1, so that the entire area of ​​the upper surface side of the workpiece 1 corresponds to each cathode portion 7d by relative rotation with respect to the workpiece 1. Note that it is sufficient that the cathode 7 corresponds to the entire workpiece 1 by relative movement such as rotation and oscillation (described later) of the workpiece 1, so that, for example, only one of the pair of cathode portions 7d in FIG. 2 may be provided.

[0028] The cathode 7 is fixed to the lower side of the support member 21 via an insulating mounting member (not shown), and a power supply member 36 is fixed to the support member 21, penetrating the support member 21 and protruding upward. The power supply member 36 is connected to the negative potential terminal of the DC power supply 9 via a negative potential power supply line 37.

[0029] The gap between the workpiece 1 and the cathode 7 is a minute gap S of 1 mm or less, preferably 500 μm or less. Hereinafter, this gap will be referred to as the minute gap S, but this does not refer to a gap of a specific size. During power supply, a closed circuit is formed between the DC power source 9, the anode 6, and the cathode 7 via the workpiece 1 and the electrolyte W.

[0030] The electrolyte supplying means 8 is arranged on the opposite side of the grinding wheel 5 from the anode 6 and the cathode 7 to the workpiece 1 side by supplying the electrolyte W from the electrode 6, 7 side of the anode 6 and the cathode 7 to form a layer of the electrolyte W between the workpiece 1, the anode 6 and the cathode 7.

[0031] This electrolyte supply means 8 has a pair of supply ports 41 arranged facing downward, a supply pipeline 43 that supplies electrolyte W from the supply source 34 to the supply ports 41, and a guide tool 44 that receives electrolyte W from the supply port 41 and guides it from the anode 6 and cathode 7 side onto the workpiece 1.

[0032] The supply ports 41 are disposed approximately symmetrically with respect to the line segment X, and are fixed so as to be vertically adjustable by adjustment means 42 such as nuts provided on both the upper and lower sides of the bracket 23. Note that the supply ports 41 may be disposed in plurality or may be one.

[0033] The guide tool 44 includes a peripheral wall portion 45 that surrounds the supply port 41 and a receiving portion 46 provided on the bottom side of the peripheral wall portion 45, and a guide port 47 that opens to the workpiece 1 side is provided in the peripheral wall portion 45. The guide tool 44 is fixed to the underside of the support member 21. The guide port 47 of the peripheral wall portion 45 is almost entirely blocked by the holding case 14 of the anode unit except for the lower side, and the electrolyte W is supplied onto the workpiece 1 through between the underside of the holding case 14 of the anode unit and the receiving portion 46.

[0034] The electrolyte supplying means 8 may supply the electrolyte W onto the workpiece 1 through the outer periphery of the holding case 14 of the anode unit. A notch 49 is provided in the guide port 47 of the receiving part 46 so as not to interfere with the anode 6. The supply port 41 of the electrolyte supplying means 8 is attached to the bracket 23, and the guide tool 44 is attached to the support member 21, but the entire electrolyte supplying means 8 may be attached to the support member 21.

[0035] The power supply lines 19, 37, the air pipe 32, and the supply pipe 43 have appropriate flexibility so as not to impede the swinging, lifting, and other movements of the anode 6, the cathode 7, the electrolyte supply means 8, etc. The support member 21, the bracket 23, and the guide 44 are made of insulating materials.

[0036] It is sufficient for the anode 6, cathode 7, and electrolyte supplying means 8 to be positioned between the grinding wheel 5 and the electrolyte supplying means 8, and it is not necessary to arrange the anode 6, cathode 7, and electrolyte supplying means 8 in a substantially straight line on the line segment X. The anode 6, cathode 7, and electrolyte supplying means 8 may be attached to a common support member 21, or may be attached to separate members so as to be individually movable.

[0037] The electrolyte supplying means 8 may be of a disposable type in which the electrolyte W applied to the workpiece 1 is discarded without circulating after each grinding, or of a circulating type in which the electrolyte W used once in grinding is collected at an appropriate location, such as downstream of the workpiece rotating device 2, purified by filtering or chemical reaction processing, and then circulated and supplied again to the workpiece 1. Therefore, the supply of the electrolyte W in this embodiment includes a case in which the electrolyte W is applied to the workpiece 1 and allowed to flow as is, and a case in which the electrolyte W once applied to the workpiece 1 is collected, purified, circulated, and applied again to the workpiece 1.

[0038] The amount of the electrolyte W supplied is at least an amount that can fill the gap between the anode 6 and the cathode 7 and the workpiece 1 during grinding. Therefore, it is sufficient that the electrolyte W accumulates at least between the anode 6 and the cathode 7 and the workpiece 1. The electrolyte W supplied from the anode 6 and the cathode 7 to the periphery of the workpiece 1 can be an electrolytic coolant such as water that is poured to cool the grinding heat of the grinding wheel 5 and to wash away grinding debris. Therefore, the electrolyte W can be any liquid that can pass a direct current, and a water-soluble coolant liquid or city water can be used.

[0039] The gap between the cathode 7 and the workpiece 1 is set to a small gap S necessary for the workpiece 1 on the workpiece rotating device 2 to rotate about the vertical axis 2a without coming into contact with the cathode 7. Therefore, the electrolyte W poured onto the workpiece 1 accumulates in the small gap S above the workpiece 1 and flows outward due to the centrifugal force of the workpiece 1. In addition, when the anode 6 is in contact with the workpiece 1, it is desirable that a film of the electrolyte W is formed between them, although there is a pressure from the coil spring 30.

[0040] When grinding the workpiece 1, the workpiece rotation device 2 with the workpiece 1 attached to its upper surface is rotated in the direction indicated by arrow a, and the upper unit U1, which includes the grinding wheel 5, anode 6, cathode 7, electrolyte supply means 8, etc., is moved toward the processing position, and then the upper unit U1 is lowered to a predetermined position.

[0041] For example, when the upper unit U1 is moved between the retracted position and the machining position, the entire power supply device including the anode 6, cathode 7, etc. is held in a raised position above the workpiece 1. At this raised position, as shown in Fig. 5(a), the cathode 7 rises and separates from the workpiece 1, while the anode 6 is pushed down by the pressure of the coil spring 30 and lowers to a position where the piston portion 28 of the anode 6 abuts against the bush 27 and is restricted. At this time, the air in the cylinder chamber 31 is vented.

[0042] When grinding of the workpiece 1 by the grinding wheel 5 starts, the power supply device is lowered until a minute gap S is formed between the cathode 7 and the workpiece 1, as shown in Fig. 5(b). If the control valve 33 is operated to release the air from the cylinder chamber 31 at this time, the protrusion 29 at the lower end of the anode 6 begins to contact the upper surface of the workpiece 1 as shown in Fig. 3 due to the lowering of the power supply device, and the coil spring 30 of the pressure applying means 16 contracts as the power supply device is lowered, and the pressure applying means 16 applies pressure to press the anode 6 against the workpiece 1. This creates a contact state in which the anode 6 contacts the upper surface of the workpiece 1 with a predetermined pressure.

[0043] Conversely, when the power supply device is in the raised position, air can be supplied to the cylinder chamber 31 to raise the anode 6, and the power supply device can be lowered until there is a minute gap S between the cathode 7 and the workpiece 1. After that, the air can be released from the cylinder chamber 31 and the anode 6 can be pressed against the workpiece 1 by the pressure of the coil spring 30.

[0044] When the anode 6 is pressed against the workpiece 1, the anode 6 is pushed back relatively against the coil spring 30, creating a gap between the piston portion 28 of the anode 6 and the upper end of the bush 27, and a gap between the piston portion 28 and the lower end of the anode holder 15. In the state shown in Fig. 3, by adjusting the air pressure in the cylinder chamber 31, the air pressure and the amount of pressure applied by the coil spring 30 can be offset, making it possible to adjust the force pressing the anode 6 against the workpiece 1. Therefore, the pressure applied to the anode 6 can be appropriately adjusted according to the state of the oxidation reaction on the upper surface side of the workpiece 1.

[0045] When air is supplied to the cylinder chamber 31 while the anode 6 is in contact with the workpiece 1, the anode 6 and the power supply member 18 rise against the pressure of the coil spring 30 until the anode 6 abuts against the lower surface of the anode holder 15, as shown in Fig. 5(b). When the piston portion 28 of the anode 6 abuts against the lower surface of the anode holder 15, a gap is created between the anode 6 and the workpiece 1, and the anode 6 and the workpiece 1 are no longer in contact with each other.

[0046] Even in this non-contact state, the space between the anode 6 and the workpiece 1 is filled with the electrolyte W, so the anode 6 and the workpiece 1 maintain electrical continuity via the electrolyte W. However, compared to a contact state in which the anode 6 and the workpiece 1 are in contact with each other, electrical resistance between the anode 6 and the workpiece 1 increases, and the anodization reaction of the workpiece 1 decreases.

[0047] Therefore, in the rough grinding region immediately after starting grinding of the workpiece 1, the anode 6 is brought into contact with the workpiece 1 and power is supplied to increase the anodizing efficiency of the workpiece 1, and when the finish grinding region or spark-out region is reached at the end of grinding, the anode 6 is withdrawn from the workpiece 1 to enter a non-contact state, intentionally lowering the anodizing efficiency, and by prioritizing grinding removal by the grinding wheel 5 over grinding by anodizing, it is possible to finish the workpiece 1 into a surface with less damage from anodizing.

[0048] When grinding the workpiece 1 with the grinding wheel 6, the electrolyte W is poured from the electrolyte supply means 8 onto the upper surface of the workpiece 1 on the workpiece rotating device 2, and a direct current is passed through the electrolyte W from the anode 6 to the workpiece 1 and then to the cathode 7, thereby sequentially processing the workpiece through the steps of rough machining, finish machining, and spark-out.

[0049] When the electrolyte W is applied from the electrolyte supply means 8 to the upper surface of the workpiece 1, the electrolyte W is applied from the electrode side of the anode 6 and the cathode 7 onto the workpiece 1. This ensures that the electrolyte W flowing along the upper surface side of the workpiece 1 is supplied to the electrodes 6, 7 side. The electrolyte W on the upper surface of the workpiece 1 flows from the outer periphery of the workpiece 1 to the outer periphery of the workpiece rotating device 2 while maintaining a thin film shape due to the centrifugal force or surface tension of the workpiece 1, and penetrates into the gap between the workpiece 1 and the anode 6 and the gap between the workpiece 1 and the cathode 7, respectively, to form an electrolyte layer with a thickness corresponding to the size of each gap.

[0050] In synchronization with the supply of the electrolyte W, the power supply device is lowered to pass a direct current through the workpiece 1, and an anodized film is formed on the upper surface of the workpiece 1 by an anodizing reaction. When the grinding wheel 5 is in a rotating state, the electrolyte W also penetrates between the rotating grinding wheel 5 and the workpiece 1, and functions as a coolant.

[0051] When the grinding wheel 5, rotating around the grindstone spindle 3, is advanced in the direction of the arrow c toward the workpiece 1, the grinding wheel 5 comes into contact with the workpiece 1, and the rough grinding process of the workpiece 1 by the grinding wheel 5 begins. On the other hand, when the power supply device is lowered to a predetermined position, a minute gap S is formed between the workpiece 1 and the cathode 7, and the anode 6 comes into contact with the upper surface of the workpiece 1 due to the pressure applied by the coil spring 30, and a direct current flows from the anode 6 to the cathode 7 via the workpiece 1 and the electrolyte W.

[0052] At this time, the anode 6 is in direct contact with the top surface of the workpiece 1, and the electrical resistance between the anode 6 and the workpiece 1 is small, so that the entire area of ​​the top surface of the workpiece 1 facing the cathode 7 has a positive potential, and this positive potential area spreads over the entire surface as the workpiece 1 rotates. This allows the top surface of the workpiece 1 to be anodized efficiently, and prevents unnecessary consumption of electricity.

[0053] In addition, since the anode 6 is provided separately from the grinding wheel 5 and there is no need to pass a direct current through the grinding wheel 5, there is no anodization reaction of the grinding wheel 5 that occurs when a direct current is passed through the workpiece 1 via the grinding wheel 5, there is no wasteful consumption of power, and deterioration of the grinding wheel 5 due to anodization reaction can be prevented, so that the grinding efficiency of the grinding wheel 5 can be maintained for a long period of time and the workpiece 1 can be efficiently processed. Furthermore, since the anode 6 is made of a material softer than the workpiece 1, damage to the upper surface of the workpiece 1 by the anode 6 can be prevented even though the anode 6 slides over the upper surface of the workpiece 1.

[0054] The anode 6 is made of a material softer than the workpiece 1, and the tip of the anode 6 that comes into contact with the workpiece 1 may be flat to make surface contact with the workpiece 1, or may be curved to minimize sliding resistance by processing it into a curved shape. The tip of the anode 6 may be in rolling contact via a roller, a sphere, or the like.

[0055] Since the anode 6 is in contact with the workpiece 1 via pressure applied by the pressure applying means 16, the anode 6 can be in stable contact with the workpiece 1 with less electrical resistance than in the case where no pressure is applied. Even if the anode 6 side is damaged due to wear or the like, the anode 6 can be pushed out toward the workpiece 1 side, so that the anode 6 can be used for a long period of time and the frequency of replacement of the anode 6 can be reduced.

[0056] Furthermore, when the anode 6 comes into direct contact with the workpiece 1, a positive potential is applied directly from the anode 6 to the workpiece 1, further reducing the electrical resistance between the anode 6 and the workpiece 1. As a result, the portion of the workpiece 1 facing the cathode 7 becomes more susceptible to anodization, and the anodization of the top surface of the workpiece 1 occurs rapidly as the top side of the workpiece 1 is anodized, allowing a soft anodized film to be formed on the top surface of the workpiece 1.

[0057] Furthermore, by applying power while pressing the anode 6 against the workpiece 1 with the pressure applying means 16, the electrical resistance at the contact portion between the workpiece 1 and the anode 6 is steadily reduced, and the workpiece 1 can be efficiently ground while being anodized, improving the grindability of the upper surface of the workpiece 1, and by cutting into the grinding wheel 5, the anodized film on the surface of the workpiece 1 that has become soft due to the anodization reaction can be ground and removed. The anodized film on the upper surface of the workpiece 1 is formed more efficiently as the minute gap S between the workpiece 1 and the cathode 7 becomes smaller.

[0058] Of course, with this anodizing-assisted grinding device, it is not necessary to immerse the workpiece 1 in an electrolyte stored in a container as in the conventional device, and therefore the device as a whole can be made smaller and simpler than in the conventional device, which required a container. Also, since the anodized film is ground and removed by the grinding wheel 5 while the electrolyte W is flowing, the grinding debris can be washed away by the flowing electrolyte W. Therefore, the grinding debris can be easily collected outside the machine, and the maintenance of the device can be easily performed.

[0059] There are several ways to control the cutting of the grinding wheel 5 into the workpiece 1, including a constant speed control method that keeps the cutting speed constant, a constant load control method that keeps the cutting load constant, an arbitrary load control method that controls the cutting speed to a given rotational load, and an oxidation rate response method that controls in accordance with the anodizing rate of the surface of the workpiece 1. In the case of the arbitrary load control method, the smaller the rotational load, the faster the cutting, and when the rotational load becomes too high, the grinding wheel 5 is controlled to move away from the workpiece 1.

[0060] The electrolyte W is supplied from the sides of the anode 6 and cathode 7 that are closer to the electrodes 6, 7 by the guide tool 44. This makes it possible to reliably supply the electrolyte W between the electrodes 6, 7 and the workpiece 1 while preventing unnecessary consumption of the electrolyte W. In particular, since the rod-shaped anode 6 is arranged on the guide tool 44 side and the cathode 7 is arranged approximately parallel to the workpiece 1 on the opposite side of the guide tool 44, sandwiching the anode 6 therebetween, the electrolyte W supplied onto the workpiece 1 can smoothly penetrate into the gaps between the anode 6 and the cathode 7 and the workpiece 1.

[0061] In addition, since the guide port 47 of the guide tool 44 is blocked by the holding case 14 of the anode 6 except for a low position on the lower side, the electrolyte W is supplied onto the workpiece 1 through the underside of the holding case 14, and the electrolyte W can be supplied in a concentrated manner in the vicinity of the workpiece 1.

[0062] Furthermore, during the machining of the workpiece 1, particularly when the grinding is near or has reached the end, the anode 6 can be raised and put into a non-contact state depending on the situation at the time, thereby reducing the efficiency of anodizing the top surface of the workpiece 1 while the anode 6 is not in contact. This allows the top surface of the workpiece 1 to be finished in a state with less damage caused by anodizing.

[0063] The non-contact state of the anode 6 may continue for a predetermined time in the finishing stage or during spark-out depending on the grinding condition of the workpiece 1, or the non-contact state and the contact state may be intermittently repeated at short time intervals after the completion of rough grinding. By doing so, in either case, the upper surface of the workpiece 1 can be finished in a state with minimal damage due to anodization.

[0064] Fig. 6 illustrates a second embodiment of the present invention. This anodization-assisted grinding device is an oscillating type, and as shown in Fig. 6(a) and (b), an upper unit U1 including a grinding wheel 5, an anode 6, a cathode 7, and an electrolyte supply means 8, and a lower unit U2 including a workpiece rotation device 2 supporting a workpiece 1 are configured to be oscillated relatively in the approximate radial direction (direction of arrows d and e) of the workpiece 1 by an oscillating means (not shown).

[0065] 6, the lower unit U2 is placed in a fixed position and the upper unit U1 is moved back and forth in the oscillation direction, but the upper unit U1 may be placed in a fixed position and the lower unit U2 may be moved back and forth in the oscillation direction, or both may be moved back and forth in the opposite directions. Other configurations are the same as those of the first embodiment.

[0066] In this manner, by performing grinding processing on the workpiece 1 while oscillating the upper unit U1 and the lower unit U2 relative to each other, the upper surface of the workpiece 1 is anodized and the upper surface of the workpiece 1 is ground efficiently by the grinding wheel 5.

[0067] That is, when a cup-shaped grinding wheel 12 is used for the grinding wheel 5, the grinding position is adjusted so that the center Y of the workpiece 1 passes within the cutting width of the cup-shaped grinding wheel 12, as shown in Figure 6(a). However, since the center Y of the workpiece 1 is not under the cathode 7, the anodizing efficiency near the center Y of the workpiece 1 is extremely reduced.

[0068] However, by relatively oscillating the upper unit U1 and the lower unit U2, the vicinity of the center Y of the workpiece 1 becomes more likely to correspond to the lower side of the cathode 7 as shown in Fig. 6(b), and the anodization of the upper surface of the workpiece 1 and the grinding of the upper surface of the workpiece 1 by the cup-shaped grinding wheel 12 can be efficiently performed. Therefore, the workpiece rotating device 2 is reciprocated in the approximate radial direction of the workpiece 1 until the center Y of the workpiece 1 is located below or near the cathode 7, and the oscillating operation of the grinding wheel 5 and the cathode 7 with respect to the workpiece 1 is repeated. This has the advantage that even when the cup-shaped grinding wheel 12 is used, the overlapping amount between the workpiece 1 and the cathode 7 becomes large, significantly improving the efficiency of anodization of the workpiece 1.

[0069] If sparking occurs before the grinding process is completed, the DC power supply 9 may be turned off to stop the anodization of the upper surface of the workpiece 1, and the oscillation operation may be continued in the same state as in normal grinding.

[0070] 7 illustrates a third embodiment of the present invention. In this anodizing-assisted grinding device, the anode 6 is pressed against the workpiece 1 by the weight of the anode 6. The anode 6 is supported by a bush 27 in a holding case 14 so as to be vertically slidable on both the upper and lower sides. The anode 6 penetrates a through hole 21a of a support member 21 and protrudes upward, and a positive potential side power supply line 19 is connected to the upper end side. The anode 6 has a piston portion 28 in the middle in the vertical direction, and the piston portion 28 is disposed in a cylinder chamber 31. The piston portion 28, the cylinder chamber 31, etc. constitute the lifting means 17 in the same manner as in the first embodiment, and the cylinder chamber 31 is connected to a control valve (not shown) via an air pipe 32.

[0071] In this case, the anode 6 can be pressed against the workpiece 1 with a predetermined pressure by the weight of the anode 6, so that the anode 6 can be stably kept in contact with the workpiece 1. Furthermore, when air is fed into the cylinder chamber 31, the anode 6 is lifted via the piston portion 28, so that the anode 6 can be kept in a non-contact state with the workpiece 1.

[0072] Therefore, the pressure applying means 16 need only be capable of applying a predetermined pressure in the direction of pressing the anode 6 against the workpiece 1, and in addition to a spring type using the coil spring 30 or the like shown in the first embodiment, it may be a cylinder type using an air cylinder to press the anode 6 against the workpiece 1, or a weight type using the weight of the anode 6 itself.

[0073] 8 illustrates a fourth embodiment of the present invention. In this anodizing-assisted grinding device, a substantially V-shaped cathode 7 is used. The cathode 7 has a pair of strip-shaped cathode portions 7d made of plate-shaped conductive members, and the two cathode portions 7d are connected in a substantially V-shape at a connection portion 7e on the power supply member 36 side. The cathode 7 has a cutout portion 7c on the side opposite the grinding wheel 5, and the anode 6, electrolyte supply means 8, etc. are provided in the cutout portion 7c. The other configuration is the same as that of the first embodiment.

[0074] Even when the cathode 7 having the band-like cathode portion 7d in a substantially V-shape is used in this way, the workpiece 1 rotates around its center during grinding, so that the cathode 7 can cover the entire surface of the workpiece 1. Therefore, each time the cathode 7 passes over the workpiece 1, the portion corresponding to the cathode 7 can be anodized intermittently with high current flow efficiency, and the portion outside the cathode 7 can be anodized with low current flow efficiency. By considering the rotation speed of the workpiece 1 and the width of the cathode portion 7d according to the material of the workpiece 1 and other factors, it is possible to efficiently process the workpiece 1 while suppressing damage to the workpiece 1.

[0075] 9 to 12 show first to fourth machining examples when grinding a workpiece 1 as a fifth embodiment of the present invention. Fig. 9 shows the first machining example. In this first machining example, the entire machining process is divided into a rough machining process, a finish machining process, and a spark-out process, and in the rough machining process, electricity is passed through the anode 6 in a contact state, in the finish machining process, electricity is passed through the anode 6 in a non-contact state, and in the spark-out process, the anode 6 is in a non-contact state and electricity is stopped.

[0076] In this way, in the rough machining process, the efficiency of current flow to the workpiece 1 is increased, and the oxidation efficiency of the upper surface of the workpiece 1 is increased, so that the machining efficiency of the workpiece 1 can be improved. On the other hand, in the finish machining process, the current flow efficiency can be intentionally lowered by passing current from the non-contact anode 6 through the electrolyte W to the workpiece 1. This prevents the oxidation efficiency of the workpiece 1 from decreasing, which would leave damage due to the oxidation reaction on the surface of the workpiece 1, and also prevents the occurrence of contact marks of the anode on the surface of the workpiece 1. In the spark-out process, there are no contact marks from the anode 6, and there is no damage due to the oxidation reaction, so that the surface of the workpiece 1 can be finished well.

[0077] Figure 10 shows the second machining example. In this second machining example, the entire grinding process is divided into a rough machining process, a finish machining process, and a spark-out process, and in the rough machining process and finish machining process, the workpiece 1 is machined while electricity is still flowing while the anode 6 intermittently repeats contact and non-contact with the workpiece 1. In the rough machining process, the contact time t1 of the anode 6 with the workpiece 1 is made longer, and in the finish machining process, the contact time t2 of the anode 6 with the workpiece 1 is made shorter than in the rough machining process.

[0078] This increases the efficiency of current flow to the workpiece 1 in the rough machining process, thereby increasing the machining efficiency of the workpiece 1, but in the finish machining process, the current flow efficiency is intentionally reduced to prevent damage caused by oxidation reaction on the surface of the workpiece 1. In the spark-out process, the anode 6 is put into a non-contact state and current flow is stopped.

[0079] Fig. 11 shows a third machining example. In this third machining example, the entire machining process is divided into a rough machining process, a finish machining process, and a spark-out process, and the anode 6 is kept in contact with the anode 6 during the rough machining process and the finish machining process, and the current is increased during the current application, and decreased during the finish machining process.

[0080] As a result, the efficiency of current flow to the workpiece 1 can be increased in the rough machining process, but the efficiency of current flow to the workpiece 1 decreases in the finish machining process, preventing damage caused by oxidation reaction on the surface of the workpiece 1. In the spark-out process, the anode 6 is put into a non-contact state and current flow is stopped.

[0081] In this third processing example, the anode 6 may be in contact with the workpiece 1 from the rough processing step to halfway through the finish processing step, as shown by the dotted line, and from halfway through the finish processing step onwards, the anode 6 may be separated from the workpiece 1 and placed in a non-contact state.

[0082] Fig. 12 shows a fourth machining example. In this fourth machining example, as shown in Fig. 12(a), a plurality of anode bars 6a-6e (for example, five) are arranged on the anode 6 side corresponding to the cathode 7. Then, in the rough machining step, as shown in Fig. 12(b), all the anode bars 6a-6e are brought into contact with the workpiece 1 and electricity is passed through the many anode bars 6a-6e, and in the finish machining step, the anode bars 6b and 6d among the anode bars 6a-6e are brought into a non-contact state to reduce the number of anode bars 6a, 6c, and 6e in contact.

[0083] This can increase the machining efficiency of the workpiece 1 in the rough machining process, but reduces the current flow efficiency of the workpiece 1 in the finish machining process, preventing damage due to oxidation reaction on the surface of the workpiece 1. In the spark-out process, all the anode bars 6a-6e are put into a non-contact state and current flow is stopped. It is preferable that the relationship between the multiple anode bars 6a-6e and the cathode 7 is such that current flows approximately evenly between each of the anode bars 6a-6e and the cathode 7, regardless of whether the number of anode bars is increased or decreased.

[0084] The processing examples are not limited to these first to fourth processing examples, and it goes without saying that there are many processing procedures depending on the processing conditions of the workpiece 1. For example, it is also possible to use the oscillation operation of the second embodiment in combination with any of the first to fourth processing examples.

[0085] Alternatively, the rough machining process may be divided into a first stage and a second stage, in which machining with high current flow efficiency of the workpiece 1 is performed, such as by contacting the anode 6 with the workpiece 1 and passing current therethrough, and in the next second stage, machining with lower current flow efficiency than in the first stage is performed, such as by repeatedly bringing the anode 6 into and out of contact with the workpiece 1, before moving from the finish machining process to the spark-out process. Note that in the spark-out process, grinding is performed for a predetermined time with the grinding wheel 12 stopping its cutting, but this spark-out process may be omitted.

[0086] Although the embodiments of the present invention have been exemplified above, the present invention is not limited to the embodiments, and various modifications are possible within the scope of the present invention. For example, in each embodiment, a flow-type anodizing-assisted grinding device in which the electrolyte W is flowed over the workpiece 1 or the like is exemplified, but the present invention can be similarly adopted in an anodizing-assisted grinding device in which the workpiece 1, the anode 6, the cathode 7, and the grinding wheel are immersed in the electrolyte W stored in a container, since it is only necessary to make it possible to supply power while pressing the anode 6 provided separately from the grinding wheel (grinding wheel 5) against the workpiece 1 by applying pressure. In other words, the present invention can be similarly adopted in both the flow-type and immersion-type electrolyte W, and is not limited to only one of them.

[0087] The power supply devices such as the anode 6 and the cathode 7, and the electrolytic solution supply means 8 are allowed to move up and down by a lifting mechanism via a support member 21, etc., and the lifting mechanism may be manual or automatic, and any mechanism such as a screw type or a cylinder type may be used. The cylinder type may be either an air pressure type or a hydraulic type. However, in terms of the machining accuracy of the workpiece 1, it is preferable to use a lifting mechanism with high positioning accuracy.

[0088] The anode 6, cathode 7, and electrolyte supply means 8 may be insulated from the support part that supports them so that they can move up and down by using an insulating material for the support member 21. The anode 6 and cathode 7 and a power supply system that supplies power to them may be made of conductors, and the electrolyte supply means 8 may be made entirely or partly of an insulating material.

[0089] The shapes of the anode 6 and the cathode 7 can be selected arbitrarily and are not limited to those in each embodiment. The contact surface of the anode 6 with the workpiece 1 may be either circular or rectangular. When the power supply member 18 is provided on the upper side of the rod-shaped anode 6, the anode 6 and the power supply member 18 may be integral or separate. On the other hand, the shape of the cathode 7 is also arbitrary. However, when at least one of the anode 6 and the cathode 7 is long in the planar direction of the workpiece 1, it is desirable that the electrical resistance between the anode 6 and the cathode 7 is approximately the same at any position. Since the anode 6 comes into contact with the workpiece 1 and the surface of the workpiece 1 facing the cathode 7 is anodized, it is desirable that the cathode 7 is wider than the anode 6 in terms of processing efficiency.

[0090] The pressurizing means 16 for applying pressure to the anode 6 may utilize a coil spring 30 or its own weight, as well as the elastic force of rubber or other elastic body, air pressure, or the magnetic force of a magnet. The lifting means 17 may also be of any type, similar to the pressurizing means 16. For example, a magnetic lifting means 17 may be used to move the anode 6 up and down by magnetic force. In that case, the lifting means 17 may also serve as part or all of the biasing means 16.

[0091] It is desirable for the anode 6 to be a conductive material that is softer than the workpiece 1, but as long as it does not leave any contact marks or the like on the workpiece 1, a material that is equal in hardness to the workpiece 1 or harder than the workpiece 1 may be used for the anode 6.

[0092] In the embodiment, a non-conductive grinding wheel is used, but a conductive one may be used. When a conductive grinding wheel is used, it is preferable to prevent the direct current from the anode 6 from flowing to the grinding wheel side.

[0093] When supplying electricity via the anode 6, the oxidation reaction on the upper surface of the workpiece 1 can be precisely controlled by bringing the anode 6 into contact with the workpiece 1 or separating it from the workpiece 1 according to the processing status of the workpiece 1 (amount removed by the grindstone). This allows the workpiece 1 to be processed efficiently and prevents an oxide layer from remaining on the upper surface of the workpiece 1.

[0094] Supplying power via the anode 6 has the advantage of increasing the options for grinding wheels, since it is not necessary to use a conductive grinding wheel 5. Also, when using the grinding wheel as the anode, the anode cannot be switched between contact and non-contact with the workpiece 1, so adjustment of the oxidation reaction on the upper surface of the workpiece 1 was limited to controlling the current value, but by combining contact and non-contact of the anode 6 with the workpiece 1, the options increase.

[0095] The electrolyte W may be supplied through the grinding wheel spindle 3. In addition, when the electrolyte W is supplied by providing a supply port 41 separately from the anode 6, the anode 6, the cathode 7, and the supply port 41 may be arranged in a positional relationship different from that of the first embodiment, such as arranging the supply port 41 so as to point to the intermediate portion between the anode 6 and the cathode 7. However, it is necessary to fill the space between the anode 6 and the cathode 7 and the workpiece 1, and the surface of the workpiece 1 with the electrolyte W. When the cathode 7 is made flat, a plurality of grooves may be provided on the surface of the cathode 7 facing the workpiece 1 so that the electrolyte W can easily flow between the cathode 7 and the workpiece 1. This allows fresh electrolyte W to be constantly supplied without old electrolyte remaining between the cathode 7 and the workpiece 1, which is expected to prevent a decrease in electrolysis efficiency. [Explanation of symbols]

[0096] 1 Workpiece 2 Workpiece rotation device 5 Grinding Wheel 6 Anode 7 Cathode 8 Electrolyte supply means 9 DC power supply 16 Pressurization means 17 Lifting means W Electrolyte

Claims

1. 1. An anodization-assisted grinding device that generates an anodized film on a surface of a workpiece by passing a direct current between an anode, a cathode, and the workpiece through an electrolyte, and grinds the anodized film with a grinding wheel, The anode, which is provided separately from the grinding wheel, is pressed against the workpiece by applying pressure while power is being supplied. An anodizing-assisted grinding device comprising:

2. The anode is a conductive material that is softer than the workpiece.

2. The anodizing-assisted grinding apparatus according to claim 1 .

3. The electrolyte is supplied from the electrode side of the anode and the cathode.

3. The anodizing-assisted grinding device according to claim 1 or 2.

4. A step of generating an anodized film on a surface of a workpiece by passing a direct current between an anode, a cathode, and the workpiece through an electrolyte; and grinding the anodized coating with a grinding wheel, The anode, which is provided separately from the grinding wheel, is pressed against the workpiece by applying pressure while power is being supplied.

1. An anodizing-assisted grinding method comprising the steps of:

5. The anode is controlled to be in contact with the workpiece or in a non-contact state depending on the stage of grinding the workpiece. The anodizing-assisted grinding method according to claim 4 .

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